Field of the Invention
The present invention relates to a one-way clutch that biases needles by magnetic force, and an image forming apparatus, such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these multiple functions, equipped with such one-way clutch.
Description of the Related Art
In an image forming apparatus, a configuration is known where a one-way clutch is provided on a conveyance roller conveying a recording material such as a sheet, the one-way clutch allowing the conveyance roller to relatively rotate only in one direction with respect to the shaft.
The one-way clutch has needles, i.e., rollers, respectively arranged in a plurality of wedged spaces formed between the housing and the shaft. The one-way clutch is configured such that the housing is only relatively rotated in one direction with respect to the shaft by biasing the needles toward a direction where the wedged spaces are narrowed. A configuration is known where magnetic force of the magnets is utilized in the arrangement for biasing the needles.
For example, Japanese Examined Patent Publication No. 6-54134 proposes a configuration where biasing members formed of magnetic bodies, i.e., magnets, are arranged at even intervals in a circumferential direction, and biasing a roller by magnetic force, and supporting the shaft by the biasing members.
However, the configuration disclosed in Japanese Examined Patent Publication No. 6-54134 has the following problems. A roller is biased by the magnetic force of biasing members. At this time, depending on the magnetized positions of the biasing members, it may not be possible to provide sufficient attraction force to the biasing members to attract the roller, and transmission of drive may be unstable. This problem is especially obvious in a case where inexpensive magnets having weak magnetic forces are used.